T1-weighting in Steady-State FLASH MRI-Diffusion Is Not Only Supportive but Mandatory for the Contrast.

Bibliographic Details
Title: T1-weighting in Steady-State FLASH MRI-Diffusion Is Not Only Supportive but Mandatory for the Contrast.
Authors: Weinmüller S; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany., Chellapandian DC; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.; Department of Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.; Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany., Endres J; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany., Leupold J; Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany., Gritsch F; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany., Wagner F; Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany., Schneider R; Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany., Zaiss M; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.; Department of Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
Source: Magnetic resonance in medicine [Magn Reson Med] 2026 Oct; Vol. 96 (4), pp. 1789-1797. Date of Electronic Publication: 2026 Jun 21.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: Wiley Country of Publication: United States NLM ID: 8505245 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1522-2594 (Electronic) Linking ISSN: 07403194 NLM ISO Abbreviation: Magn Reson Med Subsets: MEDLINE
Imprint Name(s): Publication: 1999- : New York, NY : Wiley
Original Publication: San Diego : Academic Press
MeSH Terms: Brain*/diagnostic imaging , Diffusion Magnetic Resonance Imaging*/methods , Image Processing, Computer-Assisted*/methods , Magnetic Resonance Imaging*/methods, Silicone Oils/chemistry ; Cerebrospinal Fluid/diagnostic imaging ; Phantoms, Imaging ; Computer Simulation ; Humans ; Algorithms ; Diffusion ; Printing, Three-Dimensional
Abstract: Purpose: FLASH imaging is widely assumed to produce a T1-weighted steady-state contrast using RF- and gradient-spoiling. We observed substantial overestimation of CSF signals in simulations, when diffusion was neglected and realistic proton density was applied. This work investigates the role of diffusion in steady-state FLASH contrast formation and its implications for simulation-based modeling and measurement.
Methods: FLASH sequences were simulated using phase graph simulations using a synthetic brain phantom with and without diffusion and realistic PD values to show the contrast change. The impact of neglecting diffusion in synthetic training data was evaluated using a segmentation network trained on simulated data and tested on in vivo measurement. Experimental validation of the contrast change was performed using a 3D-printed brain phantom using silicone oil as a low-diffusivity compartment.
Results: Without diffusion, simulations showed CSF signal intensities higher than WM, resulting in a contrast change. Diffusion suppresses higher-order echoes in long T2 tissues and is essential for achieving the T1-weighted steady-state contrast. A NN trained without diffusion fails to generalize to in vivo data and measurements with silicone oil compartments confirm the contrast changes in low-diffusivity media.
Conclusion: Diffusion is essential for realistic FLASH simulations of long T2 tissues such as CSF. Steady-state FLASH contrast arises from the interplay of RF-, gradient-spoiling, and "multi-TR-relaxation-spoiling" governed by T2-decay and diffusion effects. For many quadratic phase cycling schemes, diffusion is required to obtain realistic T1-weighted contrast in MR simulations and should not be neglected in simulations or simulation-based deep learning applications.
(© 2026 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)
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Grant Information: d.hip Campus - Bavarian AIM; 500888779 Deutsche Forschungsgemeinschaft; 16SV9585 Bundesministerium für Bildung und Forschung; Competence Network for Scientific High Performance Computing in Bavaria (KONWIHR)
Contributed Indexing: Keywords: RF‐spoiling; T1‐weighted FLASH; TR‐spoiling; diffusion; gradient‐spoiling; steady‐state
Substance Nomenclature: 0 (Silicone Oils)
Entry Date(s): Date Created: 20260622 Date Completed: 20260729 Latest Revision: 20260801
Update Code: 20260801
PubMed Central ID: PMC13421012
DOI: 10.1002/mrm.70443
PMID: 42324643
Database: MEDLINE
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  Data: T1-weighting in Steady-State FLASH MRI-Diffusion Is Not Only Supportive but Mandatory for the Contrast.
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  Data: <searchLink fieldCode="AU" term="%22Weinmüller+S%22">Weinmüller S</searchLink>; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.<br /><searchLink fieldCode="AU" term="%22Chellapandian+DC%22">Chellapandian DC</searchLink>; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.; Department of Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.; Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany.<br /><searchLink fieldCode="AU" term="%22Endres+J%22">Endres J</searchLink>; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.<br /><searchLink fieldCode="AU" term="%22Leupold+J%22">Leupold J</searchLink>; Medical Physics, Department of Diagnostic and Interventional Radiology, University Medical Center Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.<br /><searchLink fieldCode="AU" term="%22Gritsch+F%22">Gritsch F</searchLink>; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.<br /><searchLink fieldCode="AU" term="%22Wagner+F%22">Wagner F</searchLink>; Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany.<br /><searchLink fieldCode="AU" term="%22Schneider+R%22">Schneider R</searchLink>; Magnetic Resonance, Siemens Healthineers AG, Erlangen, Germany.<br /><searchLink fieldCode="AU" term="%22Zaiss+M%22">Zaiss M</searchLink>; Institute of Neuroradiology, Uniklinikum Erlangen, Erlangen, Germany.; Department of Artificial Intelligence in Biomedical Engineering (AIBE), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
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  Data: <searchLink fieldCode="MM" term="%22Brain%22">Brain*</searchLink>/<searchLink fieldCode="MM" term="%22Brain+diagnostic+imaging%22">diagnostic imaging</searchLink> <br /><searchLink fieldCode="MM" term="%22Diffusion+Magnetic+Resonance+Imaging%22">Diffusion Magnetic Resonance Imaging*</searchLink>/<searchLink fieldCode="MM" term="%22Diffusion+Magnetic+Resonance+Imaging+methods%22">methods</searchLink> <br /><searchLink fieldCode="MM" term="%22Image+Processing%2C+Computer-Assisted%22">Image Processing, Computer-Assisted*</searchLink>/<searchLink fieldCode="MM" term="%22Image+Processing%2C+Computer-Assisted+methods%22">methods</searchLink> <br /><searchLink fieldCode="MM" term="%22Magnetic+Resonance+Imaging%22">Magnetic Resonance Imaging*</searchLink>/<searchLink fieldCode="MM" term="%22Magnetic+Resonance+Imaging+methods%22">methods</searchLink><br /><searchLink fieldCode="MH" term="%22Silicone+Oils%22">Silicone Oils</searchLink>/<searchLink fieldCode="MH" term="%22Silicone+Oils+chemistry%22">chemistry</searchLink> ; <searchLink fieldCode="MH" term="%22Cerebrospinal+Fluid%22">Cerebrospinal Fluid</searchLink>/<searchLink fieldCode="MH" term="%22Cerebrospinal+Fluid+diagnostic+imaging%22">diagnostic imaging</searchLink> ; <searchLink fieldCode="MH" term="%22Phantoms%2C+Imaging%22">Phantoms, Imaging</searchLink> ; <searchLink fieldCode="MH" term="%22Computer+Simulation%22">Computer Simulation</searchLink> ; <searchLink fieldCode="MH" term="%22Humans%22">Humans</searchLink> ; <searchLink fieldCode="MH" term="%22Algorithms%22">Algorithms</searchLink> ; <searchLink fieldCode="MH" term="%22Diffusion%22">Diffusion</searchLink> ; <searchLink fieldCode="MH" term="%22Printing%2C+Three-Dimensional%22">Printing, Three-Dimensional</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Purpose: FLASH imaging is widely assumed to produce a T<subscript>1</subscript>-weighted steady-state contrast using RF- and gradient-spoiling. We observed substantial overestimation of CSF signals in simulations, when diffusion was neglected and realistic proton density was applied. This work investigates the role of diffusion in steady-state FLASH contrast formation and its implications for simulation-based modeling and measurement.<br />Methods: FLASH sequences were simulated using phase graph simulations using a synthetic brain phantom with and without diffusion and realistic PD values to show the contrast change. The impact of neglecting diffusion in synthetic training data was evaluated using a segmentation network trained on simulated data and tested on in vivo measurement. Experimental validation of the contrast change was performed using a 3D-printed brain phantom using silicone oil as a low-diffusivity compartment.<br />Results: Without diffusion, simulations showed CSF signal intensities higher than WM, resulting in a contrast change. Diffusion suppresses higher-order echoes in long T<subscript>2</subscript> tissues and is essential for achieving the T<subscript>1</subscript>-weighted steady-state contrast. A NN trained without diffusion fails to generalize to in vivo data and measurements with silicone oil compartments confirm the contrast changes in low-diffusivity media.<br />Conclusion: Diffusion is essential for realistic FLASH simulations of long T<subscript>2</subscript> tissues such as CSF. Steady-state FLASH contrast arises from the interplay of RF-, gradient-spoiling, and "multi-TR-relaxation-spoiling" governed by T<subscript>2</subscript>-decay and diffusion effects. For many quadratic phase cycling schemes, diffusion is required to obtain realistic T<subscript>1</subscript>-weighted contrast in MR simulations and should not be neglected in simulations or simulation-based deep learning applications.<br /> (© 2026 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)
– Name: Ref
  Label: References
  Group: RefInfo
  Data: M. Markl and J. Leupold, “Gradient Echo Imaging,” Journal of Magnetic Resonance Imaging 35, no. 6 (2012): 1274–1289, https://doi.org/10.1002/jmri.23638.<br />A. Haase, J. Frahm, D. Matthaei, W. Hanicke, and K.‐D. Merboldt, “FLASH Imaging. Rapid NMR Imaging Using Low Flip‐Angle Pulses,” Journal of Magnetic Resonance (1969) 67, no. 2 (1986): 258–266, https://doi.org/10.1016/0022‐2364(86)90433‐6.<br />A. P. Crawley, M. L. Wood, and R. M. Henkelman, “Elimination of Transverse Coherences in FLASH MRI,” Magnetic Resonance in Medicine 8, no. 3 (1988): 248–260, https://doi.org/10.1002/mrm.1910080303.<br />Y. Zur, M. L. Wood, and L. J. Neuringer, “Spoiling of Transverse Magnetization in Steady‐State Sequences,” Magnetic Resonance in Medicine 21, no. 2 (1991): 251–263, https://doi.org/10.1002/mrm.1910210210.<br />W. T. Sobol and D. M. 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              Text: 2026 Oct
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